Internal combustion engine



Nov. s, 1938. M. WARE 2,136,162

INTERNAL COMBUSTION ENGINE Filed Jan. 30, 1935 Patented Nov. 8, 1938UNITED STATES PATENT OFFICE Marsden Ware, Detroit,

Mich., assignor to Packard Motor Car Company, Detroit, Mich, acorporation of Michigan Application January 30, I935, Serial No. 4,060

6 Claims.

This invention relates to pistons for internal combustion engines andmore particularly to pistons for use in such engines.

One object of the present invention is to produce a novel and improvedpiston for internal combustion engines which is light in weight, strongand durable in construction and having a skirt which is capable ofexpansion under the high temperatures to which the piston is subjectedin operation without undue friction against the walls of the cylinderand which will prevent the passage between the same and the cylinderwall of a greater quantity of oil than that required for properlubrication at any point in the periphery of the piston.

Another object 01' the invention is to produce an improved pistonconstruction having a skirt which is integrally attached to the head toform a structure sufficiently rigid to withstand in a reliable mannerthe strain of piston operation, which is shaped to fit closely to thecylinder wall entirely about the periphery of the piston at one or morepoints axially thereof and which will yield when expanded under the hightemperatures within the engine cylinder.

With the above and other objects in view the invention consists in apiston construction embodying the novel and improved featureshereinafter described and particularly pointed out in the claims, theadvantages of which will be readily understood by those skilled in theart.

The invention will be clearly understood from the accompanying drawingillustrating constructions embodying the invention in its preferred formand the following detailed description of the constructions thereinshown.

In the drawing, Fig. l is a view partially in side elevation and partlyin vertical section illustrating an engine cylinder and a pistonembodying the invention engaging therein.

Fig. 2 is a view in horizontal section taken substantially on the line2-2 of Fig 2 with portions of the piston and cylinder broken away.

Fig. 3 is a view in horizontal section taken substantially on the line3-3 of Fig. 1.

Fig. 4 is a view in horizontal section taken substantially on the line4-4 of Fig. 1.

Fig. 5 is a view in side elevation illustrating a piston embodying theinvention having a diilerent slot arrangement than that shown in Fig. land,

Fig. 6 is a view in side elevation illustrating a piston having a stilldifferent slot arrangement.

In the form of the invention shown in the drawing, the invention isembodied in a piston indicated as a whole at 2 and shown in Figs. 1 to(Cl. 309-1l) 4 inclusive engaging in the cylindrical bore in an enginecylinder 3. 4 indicates a connecting rod and 5 a piston pin forconnecting the piston with one end of the connecting rod. The piston isprovided with a head 6 formed with peripheral grooves I in which arefitted piston rings 8 and a skirt 9 integrally attached directly to thehead, preferably about the greater part of the periphery of the piston.The piston is provided with piston pin bosses Ill in which the pistonpin 5 engages. These bosses are integrally connected with the portion ofthe skirt extending between the same and the head and ribs, one of whichis indicated at H, extend from the bosses along the inside of the skirtto the head to give added strength. The bosses are each directly andintegrally connected at the sides with the upper part of the skirt andat the bottom with the portion of the skirt below the same. Theperipheral portion of the piston adjacent the piston pin bosses isrelieved as indicated at I! to provide ample clearance at all timesbetween these portions of the piston and the cylinder wall The head isseparated from the skirt on one side of the piston by a transverse slotI3 and the skirt is formed with a longitudinal slot I4 extendingdownwardly from the slot l3 and terminating at some distance from thelower end of the skirt. The transverse slot I3 reduces the heatconduction between the head and the skirt and the longitudinal slot l4together with the slot i3 allow the upper portion of the skirt to yieldduring the expansion of the skirt.

In order to enable the portion of the skirt between the piston pinbosses and the lower end thereof to yield when expanded against thecylinder wall under the high temperatures to which the piston issubjected in the engine cylinder, the skirt, in a zone between saidbosses and the lower end portion thereof, is given a cross sectionnormal to the piston axis in which the periphery has the form of aconvex curve and the diameter of the skirt in one direction issubstantially greater than another diameter perpendicular thereto. Informing the piston skirt with a zone of this cross section, the bearingsurface is preferably made generally elliptical or oval the termelliptical not being restricted to a bearing surface having the form ofa mathematical ellipse. In the construction shown, the skirt is madeelliptical in cross section normal to the axis in a zone extending oneach side of the line 3-3 of Fig. l on which the section shown in Fig. 3is taken. In forming this elliptical cross section the minor diameter oraxis of the piston in said zone is preferably located substantiallyparallel with the axis of the piston pin bosses. The skirt along saidelliptical zone is arranged to engage the wall of the cylinder at therespective ends of the major diameter or axis and for some distance oneach side of the ends of said axis and to leave a clearance at andadjacent the respective ends of the minor axis as shown in Fig. 3. Thisclearance varies with the expansion of the piston in the cylinder.

The difference in the length of the major and minor axes of the pistonin this zone may differ in pistons of different size and also may bevaried in pistons of the same size. For example, it is proposed to formthe cross section in this zone of a piston having a diameter of 3 at thebottom of the skirt so the major axis is at least .005 to .007 of aninch greater than the minor axis. The difference in the length of themajor and minor axes may, however, be made as much as .012 of an inch oreven more if desired.

To give the lower portion of the skirt a bearing against the cylinderwall about the entire periphery thereof and to prevent the passage ofoil between the skirt and said wall in excess of that required forproper lubrication, the end portion of the skirt remote from the head ismade substantially circular in cross section normal to the axis and isarranged to fit closely to said wall at all points in the periphery ofthe skirt. The skirt is preferably made substantially circular in crosssection in a relatively narrow zone at the lower end thereof. This zone,however, may be given any width to furnish the desired bearing area forengagement with the wall of the cylinder and to produce the desiredresults in the forming of an oil film between the skirt and said wall.Fig. 4 is a section of the piston and cylinder taken through this zone.This portion of the skirt will act to spread the oil in a thinlubricating film over the inner surface of the cylinder and the loweredge of the skirt will collect the excess of oil and cause the same tobe drained of! at the bottom of the cylinder.

The zone of the piston skirt having an oval or elliptical cross sectionpreferably blends into the zone having a circular cross section as shownin Figs. 1, 5 and 6. Thus the minor axis of the skirt in this zonegradually increases from the upper to the lower portion of said zone andbecomes substantially equal to the major axis at the lower end of saidzone as shown in Fig. 1.

To enable the lower end portion of the skirt to expand without bindingagainst the walls of the cylinder, the skirt is formed with one or moreslots i 5 extending upwardly from the lower end of the skirt preferablyto a point or points substantially opposite the lower end of the slot l4peripherally of the piston. Figs. 1, 2 and 3 show these slots located indifferent positions about the periphery of the piston skirt. In theconstruction shown in Fig. 1 the piston is provided with a single slotl5 located on the same side of the skirt as the slot l4 and generally inline with the slot I4, axially of the piston. In the construction shownin Fig. 5 the piston is provided with two slots l5, each located.substantially degrees from the slot ll about the periphery of thepiston. In the construction shown in Fig. 6, the piston is provided witha single slot I! located on the side thereof opposite the slot II andsubstantially degrees from the slot ll about the periphery of thepiston.

In addition to the advantages above pointed out, the above constructionresults in a piston which is strong, sturdy and durable and in which theskirt, because of its rigid connection with the head except at the pointat which the slot I3 is formed, is not liable to get out of alignmentaxially with the head. The strength of the construction enables thepiston to be made lighter than certain constructions now in extensiveuse upon automobile engines. The skirt is sufficiently yielding toprevent the same from binding against the cylinder wall when expandedand at the same time has the stiffness required to enable the same towithstand in a reliable manner the strains to which it is subjected inoperation. The slots l5 allow the lower end portion of the skirt, whenexpanded against the cylinder wall 2, to yield sufficiently to preventthe same from binding or exerting undue friction. The slots, however,extend only a short distance upwardly from the end of the piston and thelower end portion of the piston is therefore fairly stiff.

As the increase in the length of the minor axis of the skirt in the zonehaving an oval or elliptical cross section tends to diminish theyieldability of the skirt from the upper to ward the lower portion ofsaid zone, the slots l5 tend to give a flexibility to this part of theskirt progressively increasing in the said direction.

It is to be understood that the invention is not limited to theparticular construction of the illustrated embodiment of the inventionbut that the said construction is merely illustrative of the inventionand that the invention may be embodied in other forms within the scopeof the claims.

Having explained the nature and object of the invention and havingspecifically described a construction embodying the invention in itspreferred form what is claimed is:

l. A piston for internal combustion engines having a head, a skirtintegrally connected at its upper end directly with the head, and pinbosses integrally attached directly to the skirt, the skirt having acircular peripheral bearing surface at the end remote from the head,said skirt having its periphery relieved about the pin bosses and theperipheral bearing surface intermediate the circular bearing surface andthe relieved portions being elliptical in cross section normal to theaxis of the piston, the elliptical bearing surface blending into thecircular bearing surface axially of the piston, said skirt havingaxially extending slots therein terminating short of each other in theelliptical cross sectional portion thereof.

2. A piston for internal combustion engines comprising a head, a skirtintegrally connected at one end with the head and partially separatedtherefrom by a slot extending transversely of the piston axis, and apair of aligned pin bosses on the skirt, a slot extending axially of theskirt between and co-extensive with the pin bosses and connected withthe transverse slot, and another slot extending axially in the skirtfrom the end opposite the head to a point short of the other axiallyextending slot, said skirt being circular in cross section at the endremote from the head and ovate in cross sectional portion adjacent toand between the axially extending slots.

3. A piston for internal combustion engines comprising a head, a skirtintegrally connected at one end with the head and partially separatedtherefrom by a slot extending transversely of the piston axis, and apair of aligned pin bosses on the skirt, a slot extending axially of theskirt between and co-extensive with the pin bosses and connected withthe transverse slot, and another slot extending axially in the skirtfrom the end opposite the head to a point short of the other axiallyextending slot, said axially extending slots being spacedcircumferentially in the skirt more than 90, said skirt being circularin cross section at the end remote from the head and ovate in crosssectional portion adjacent to and between the axially extending slots.

4. A piston for internal combustion engines comprising a head, a skirtintegrally connected at its upper end directly with the head andpartially separated therefrom by a slot extending transversely of thepiston axis, and a pair of aligned pin bosses extending interiorly ofsaid skirt and formed therewith, said skirt having a slot extendingaxially thereof between the pin bosses and co-extensive therewith andconnected with the transverse slot, said skirt having another axiallyextending slot spaced circumferentially from the first mentioned axiallyextending slot and extending from the end of the skirt remote from thehead to a point short of the first mentioned axially extending slot, theperiphery of said skirt surrounding said piston bosses being relieved,the peripheral surface at the end of said skirt remote from the headbeing circular and the peripheral surface of said skirt adjacent to andbetween the axially extending slots being formed oval in cross section.

5. A piston for internal combustion engines comprising a head, a skirtintegrally connected at one end directly to the head and partiallyseparated therefrom by a circumferentially extending slot, and a pair ofaligned piston bosses extending interiorly of said skirt and formedtherewith, the peripheral surface of said skirt being relieved in thezones of the piston pin bosses, said skirt having a slot therethroughextending axially between the pin bosses and from the circumfercntialslot to a point substantially on a circumferential line with therelieved peripheral zones of the skirt remote from the head, said skirthaving another slot therethrough extending axially from one of therelieved peripheral zones to the skirt end remote from, the head, saidskirt being circular in cross section at the end remote from the headand ovate in cross sectional portion adjacent to and between the axiallyextending slots.

6. A piston for internal combustion engines comprising a head, a skirtintegrally connected at one end directly with the head and partiallyseparated therefrom by a circumferentially extending slot, and a pair ofaligned piston bosses extending interiorly of said skirt and formedtherewith, said skirt having a slot extending axially thereof betweenthe piston bosses and co-extensive therewith and connected with thecircumferentially extending slot, the periphery of said skirt in thezones of the piston bosses being relieved, the peripheral surface at theend of said skirt remote from the head being circular and the peripheralsurface of said skirt from the circular peripheral surface to theadjacent relieved portions being ovate in cross section, and said pistonskirt having slots therethrough extending axially from the relievedperipheral zones to the end of the skirt remote from the head.

MARSDEN WARE.

